Work planned for this upcoming granting period will involve the following: (1) Determine the normal growth curves for the olfactory bulb and olfactory epithelium in culture by monitoring a number of biochemical parameters including H3-thymidine incorporation in DNA and the activities of thymidine kinase, DNA polyneurase II, thymidylate synthetase, riboneclueotide reductase, and ornithine decarboxylase. (2) Determine the effect of added protein and peptide fractions from olfactory tissue taken at various times subsequent to nerve section on the mitotic activity of cultured epithelium. (3) Determine the role of cyclic nucleotide in controlling this process. (4) Determine the effects of added extracts to the levels of olfactory markers in epithelial cultures. Is there correlation to changes in mitotic activity? (5) A coorgan culture system of olfactory bulb and olfactory epithelium will make possible experimental manipulations, observations, and conclusions which could not be accomplished using the epithilial culture system. This system will permit the observation of directed oxonal growth from epithelium to bulb. Nerve section can be performed in culture and will thus make it possible to observe and photograph the entire process of retrograde degeneration and subsequent mitosis, differentiation, and neuronal replacement. It will be possible to ascertain the necessity of bulbar presence for active mitosis, differentiation, and axon growth. (6) Changes in the pattern of peptides, soluble proteins, and membrane proteins will be monitored throughout the time course of degeneration and regeneration. (7) By using the sensitive detection technique of autoradiography and the separation techniques of two dimensional TLC and a combination of two dimensional isoelectric focusing and gradient or SDS electrophoresis, peptides, soluble and membrane bound proteins which are specific to the olfactory neurons will be isolated. (8) The effects of these compounds on the processes of mitosis, differentiation, and innervation will be monitored use test tissue culture systems.